The Human Immunology Core will support the therapeutic trial and also support the pre-clinical and basic studies. The Core will organize and store PBMC from the trial and perform four primary assays for both the University of North Carolina, Chapel Hill and the Massachusetts General Hospital trial sites. These assays are 1) measurement of lymphocyte subsets in patient blood, 2) a Iymphoproliferative response assay to measure the ability of CD4 helper T -cells to respond to HIV antigens, 3) assays to measure the cellular immunity to HIV, such as CTL assay or assays to detect intracellular interferon gamma production after antigenic stimulation, and 4) a neutralization assay (performed by David Montefiori). These data will be crucial to the success of the trial, and combined with other information, will yield a comprehensive analysis of the clinical trial.